In a ink-jetting recording apparatus such as an ink-ejecting printer or an ink-jetting plotter (a kind of liquid ejecting apparatus), a recording head (head member) can move in a main scanning direction, and a recording paper (a kind of medium to which liquid is ejected) can move in a sub-scanning direction perpendicular to the main scanning direction. While the recording head moves in the main scanning direction, a drop of ink can be ejected from a nozzle of the recording head onto the recording paper. Thus, an image including a character or the like can be recorded on the recording paper. For example, the drop of ink can be ejected by causing a pressure chamber communicating with the nozzle to expand and/or contract.
The pressure chamber may be caused to expand and/or contract, for example by utilizing deformation of a piezoelectric vibrating member. In such a recording head, the piezoelectric vibrating member can be deformed based on a supplied driving-pulse in order to change a volume of the pressure chamber. When the volume of the pressure chamber is changed, a pressure of the ink in the pressure chamber may be changed. Then, the drop of ink is ejected from the nozzle.
In such a recording apparatus, a driving signal consisting of a series of a plurality of pulse-waves is generated. On the other hand, printing data including level data (gradation data) can be transmitted to the recording head. Then, based on the transmitted printing data, only necessary one or more pulse-waves are selected from the driving signal and supplied to the piezoelectric vibrating member. Thus, a volume of the ink ejected from the nozzle may be changed based on the level data.
It has been proposed that a plurality of ink drops whose speeds are different are joined to each other before they reach a recording paper, when the plurality of ink drops are ejected from the same nozzle based on a level data (JP Laid-Open Publication No. 8-336970 and JP Laid-Open Publication No. 59-133066). This manner can remarkably inhibit generation of ink mist, compared with a case wherein the plurality of ink drops are joined to each other after they reach the recording paper.
Recently, various pigment inks are available on the market. The pigment inks are superior in environmental resistance (water resistance and/or light resistance). On the other hand, the pigment inks have high viscosity. Thus, ink mist is likely to be generated by satellite ink drops, compared with conventional dye inks whose viscosity is low.
The inventors have found that it is effective to decrease the ejecting speed of an ink drop in order to inhibit mist generation of a pigment ink. When the ejecting speed of an ink drop is decreased, the tendency of dissociation of the ink drop is inhibited, and hence generation of satellite ink drops is inhibited.
However, when the ejecting speed of an ink drop is decreased, the ink drop reaches the recording paper less precisely. That is, regarding the ejecting speed of an ink drop, the tendency of the generation of the satellite ink drops and the precision of reach to the recording paper are contradictory.